1. Field of the Invention
The invention relates to a shifting method and particularly to a bicycle shifting method.
2. Description of Related Art
In recent years, the market for bicycles has been growing, and thus consumers are not only interested in the recreational road bicycles but also fond of the high-end racing bicycles. Generally, the bicycles are equipped with derailleurs, so as to move the chain onto different chain rings according to different terrain requirements and various consumers' needs. The derailleurs include front and rear derailleurs respectively controlling the locations of the chain on the front and rear chain rings. Due to the difference in frame structures or shifting cables, the bicycles may have different derailleurs. In addition to the mechanical derailleurs, various bicycles are equipped with electronic derailleurs.
The bicycle may be shifted by switching the location of the chain on the chain rings, and the shifting effect is relevant to the gear ratio of the front chain ring and the rear chain ring where the chain is located. The gear ratios of all front and rear chain rings of a bicycle are sequentially organized into a gear-ratio table, and the gear-ratio table is conducive to a user who intends to sequentially switch the location of the chain to be on different chain rings according to the gear-ratios. Conventionally, the speed of the bicycle is often changed in a manual manner, i.e., the controlling switch is manually adjusted to enable the front and rear derailleurs to simultaneously change the location of the chain on the first and rear chain rings. Said operation is rather complicated.
At present, in order to change the speed of the bicycle, an electronic system is often applied to adjust the controlling switch, and the controlling switch has been simplified to be a two-way switch including a speed-increasing way and a laborsaving way. Besides, a controller may be employed to control the gear ratio of the bicycle with ease. However, when the derailleurs are controlled to sequentially change the location of the chain on the chain rings according to the gear ratio, the shifting action is sometimes performed around the same location. At this time, if the adjustment of the gear ratio requires the simultaneous change to the locations of the chain on the front and rear chain rings, the repetitive changing actions may cause the front and rear derailleurs to move the chain to a great extent. Thereby, the rider's pedaling action is not smooth, and the shifting parts are likely to be damaged.